The present invention relates to a method of reducing the viscosity of fabric conditioning compositions.
It is well known to provide liquid fabric conditioning compositions which soften in the rinse cycle.
Such compositions comprise less than 7.5% by weight of softening active, in which case the composition is defined as xe2x80x9cdilutexe2x80x9d, from 7.5% to about 30% by weight of active in which case the compositions are defined as xe2x80x9cconcentratedxe2x80x9d or more than about 30% by weight of active, in which case the composition is defined as xe2x80x9csuper-concentratedxe2x80x9d.
Concentrated and super-concentrated compositions are desirable since these require less packaging and are therefore environmentally more compatible than dilute or semi-dilute compositions.
A problem frequently associated with concentrated and superconcentrated compositions, as defined above, is that the product is not stable, especially when stored at high temperatures. Instability can manifest itself as a thickening of the product upon storage, even to the point that the product is no longer pourable.
The problem of thickening upon storage is particularly apparent in concentrated and superconcentrated fabric softening compositions comprising an ester-linked quaternary ammonium fabric softening material having one or more fully saturated alkyl chains.
A further problem known to affect concentrated and super-concentrated fabric softening compositions comprising an ester-linked quaternary ammonium fabric softening material having one or more fully saturated alkyl chains is that the initial viscosity of a fully formulated composition can be very high, up to a point that the composition is substantially unpourable.
However, it is desirable to use ester-linked compounds due to their inherent biodegradability and to use substantially fully saturated quaternary ammonium fabric softening compounds due to their excellent softening capabilities and because they are more stable to oxidative degradation (which can lead to malodour generation) than partially saturated or fully unsaturated quaternary ammonium softening compounds.
Of the types of ester-linked quaternary ammonium materials known, it is desirable to use those based on triethanolamine which produce at least some mono-ester linked component and at least some tri-ester linked component since the raw material has a low melting temperature which enables the manufacturing process of the composition to occur at low temperatures. This reduces difficulties associated with high temperature handling, transport and processing of the raw material and compositions produced therefrom.
The problem of high initial viscosity and visco-stability upon storage has previously been addressed in various ways.
For instance, EP-A2-0415698 (Unilever) discloses the use of electrolytes, polyelectrolytes, or decoupling polymers to reduce the viscosity of fabric softening compositions.
It is also known that an input of energy such as milling or shearing of the product can reduce product viscosity. However, compositions produced by this approach can suffer from colloidal instability. Also, milling or shearing products in an manufacturing process on an industrial scale is time consuming and expensive.
DE 2503026 (Hoechst) discloses formulations comprising 3-12% of a softener (a mixture of non-ester quaternary ammonium compounds imidazoline group containing compounds), 1-6% of a cationic disinfectant, 0.1-5% of a lower alcohol, 0.5-5% of a fatty alcohol and 0-5% of a nonionic emulsifier.
WO 99/50378 (Unilever) relates to compositions comprising from 1 to 8% of a quaternary ammonium compound, a stabilising agent and a fatty alcohol. The fatty alcohol is present in order to thicken the dilute composition. The disclosure only relates to dilute compositions and so is not in any way directed to the problem addressed in the present invention of high temperature storage stability of concentrated compositions.
U.S. Pat. No. 4,844,823 (Colgate-Palmolive) discloses a composition comprising 3 to 20% by weight of the combination of a mixture of quaternary ammonium fabric softening compound and fatty alcohol in a weight in a weight ratio 6:1 to 2.8:1. Only non-ester quaternary ammonium compounds are exemplified and there is no disclosure or teaching of fully saturated quaternary ammonium compounds.
The prior art does not address nor given any suggestion how to overcome high initial viscosity and/or high temperature storage stability problems in concentrated compositions comprising fully hardened quaternary ammonium ester linked compounds based on triethanolamine.
WO 93/23510 (Procter and Gamble) mentions fatty alcohols and fatty acids as optional nonionic softeners and teaches that they can improve the fluidity of premix melts. There is no reference to reducing the viscosity of dispersions made from premix melts.
WO 98/49132, U.S. Pat. Nos. 4,213,867, 4,386,000, GB-A-2007734, DE 2503026, DE 3150179, U.S. Pat. Nos. 5,939,377, 93,915,867 and 3,644,203 all disclose fabric conditioning compositions comprising fatty alcohols. Fatty alcohols are known as co-softeners and for increasing the viscosity of compositions.
None of the prior art teaches that fatty alcohols can be used to prevent an increase in the viscosity of concentrated fabric conditioning compositions and/or to overcome the problem of high initial viscosity of the fully formulated composition.
The present invention seeks to address one or more of the above-mentioned problems, and, to give one or more of the above-mentioned benefits desired by consumers.
It has surprisingly been found that by incorporating a fatty component which comprises a long alkyl chain, such as a fatty alcohol or fatty acid (hereinafter referred to as xe2x80x9cfatty completing agentxe2x80x9d) into softening compositions comprising a quaternary ammonium softening material having substantially fully saturated alkyl chains, at least some mono-ester linked component and at least some tri-ester linked component, where the fatty complexing agent is present in an amount significantly greater than normally present in traditional fabric softening compositions, then the stability and initial viscosity of the composition can be dramatically improved. In particular, undesirable thickening of the composition upon storage can be avoided.
According to the present invention there is provided:
a method of thinning a fabric conditioning composition comprising (a) from 7.5 to 80% by weight of a ester-linked quaternary ammonium fabric softening material comprising at least one mono-ester linked component and at least one tri-ester linked component; the method comprising the step of adding a fatty complexing agent (b) to the composition in an amount such that the weight ratio of the mono-ester linked component of compound (a) to fatty complexing agent (b) is from 2.93:1 to 1:5.
There is further provided a method of treating fabrics comprising contacting a fabric conditioning composition prepared according to the method of the invention with fabrics in a laundry treatment process.
In the context of the present invention, the term xe2x80x9ccomprisingxe2x80x9d means xe2x80x9cincludingxe2x80x9d or xe2x80x9cconsisting ofxe2x80x9d. That is the steps, components, ingredients, or features to which the term xe2x80x9ccomprisingxe2x80x9d refers are not exhaustive.